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One of the most distinctive features of the heterosporous lycopsids is the presence of a ligule. This structure, currently found only in Isoetes and Selaginella, is comprised of a basally embedded glossopodium and a free distal tongue. Previous studies on Indian species have demonstrated small variations in glossopodia suggesting the possibility that this structure could have taxanomic use. Serial cross, paradermal, and sagittal sections of glossopodia from three different North American species, representing three ploidy levels, were made. Three-dimensional digital rendering of the glossopodia provided comparative data for the three North America species and allowed comparisons with previously published descriptions. In general, the shape of the glossopodium is similar in all three North American species. There are several structural differences among them, such as the shape of the cornua, the length of the medimoles, and the angle of the glossopodium relative to the leaf axis.
Dicksonia sellowiana spores were cultivated in mineral solution. After 30 days, young gametophytes were transferred to different substrates: soil rich in organic matter; coxim: coconut fiber; sterilized red soil; sterilized red soil with the addition of organic compost, to determine the best substrate for gametophytes' and sporophytes' development. Red soil with the addition of compost was the best system for growth. When sporophytes were 1.5–2.0 cm in height, they were transferred to pots containing sterilized red soil with the addition of organic compost and kept in the field for 42 days, under 75, 50, 10 and 3% of irradiance. The longest frond height, frond quantity, fresh and dry mass, and RGR were observed in plants growing in 10% of irradiance. Plants kept under 100% irradiance died after 3 days, and under 50% and 75% irradiance they died gradually after 30 days. The fresh mass/dry mass ratio was higher at 3% and lower at 30% irradiance. The levels of chlorophyll a, chlorophyll b and total chlorophyll were higher in the plants grown at 3% irradiance. The levels of chlorophyll did not vary between 10 and 30% irradiance, with the exception of chlorophyll a, which was lower under 30% irradiance. The chlorophyll a/chlorophyll b ratio did not vary among treatments. This study provides information for the cultivation of Dicksonia sellowiana with special attention to conservation and sustainable management.
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